The purpose of this study is to assess the test-retest reliability, sensitivity to individual variations in motor development, predictive validity, and sensitivity to intervention of a new test for use by rehabilitation specialists to assess functional motor performance in infants at high risk for developmental disability. The Test of Infant Motor Performance (TIMP Ver.3) is used to assess the postural and selective control needed by infants for 32 weeks gestational age to 4 months post term equivalent age to change positions, orient to interesting stimuli, and interact with the environment. Test-retest stability over two to three days will be assessed in 130 infants in three special care nursery settings using regression analysis. Longitudinal development on the TIMP will be assessed in infants with four different levels of risk for brain insults, including preterm infants with Grades II-IV intraventricular hemorrhage or periventricular leukomalacia and infants with documented perinatal asphyxia: 20 infants with extreme prematurity but no severe lung disease or brain insult; 20 low risk premature infants; and 20 infants low risk full term infants. Each infant will be assessed weekly from entry to the study until the age of four months post-term equivalent age to assess the sensitivity of the TIMP to varying rates of motor development in groups of infants who differ in risk for developmental disability. Predictability of the TIMP perinatal scores to neurologic outcome and to performance on the Alberta Infant Motor Scale (AIMS) at 3,6,9, and 12 months and concurrent validity of the TIMP scores with the AIMS at 3 months will be assessed. The sample in each study will include approximately equal numbers from three ethnic groups (Caucasian, African-American, Latino). Random effects regression models will be used to assess differences in developmental growth curves related to diagnostic group and AIMS outcome. Covariates will include medical complications score, age, maternal education, and ethnicity. Item analysis based on Rasch psychometric models will be used to develop a final research edition of the TIMP, to assess the potential for developing a shorter screening version of the test, to assess differential item responsivity based on ethnicity, and to describe developmental profiles based on diagnostic group.